In his first Congressional testimony about the Secret Service prostitution scandal, the agency’s director faced a grilling from skeptical Senators who raised concerns that the conduct seemed prevalent and accepted among agents and supervisors.

Nonetheless, Director Mark Sullivan left the Homeland Security and Governmental Affairs hearing room with his job intact Wednesday, as the committee’s top two Members declared that, despite his defensiveness, they have confidence in his leadership.

Still, the scandal doesn’t appear to be dying down anytime soon. Four Secret Service agents who were dismissed following an internal investigation are now suing the agency, and revelations have come to light that two Drug Enforcement Administration agents in Cartagena, Colombia, may have hired prostitutes in a separate incident, according to published reports.

At least a dozen Secret Service agents solicited prostitutes in Cartagena in advance of President Barack Obama’s visit there for an international conference on the Americas. A few military personnel have also been implicated in the scandal.

Sullivan told Senators that the April incident was an anomaly in an agency full of trustworthy agents.

“I’ve been part of this organization for 29 years and I’ve never seen anything like this in my life,” he said. “The notion that this type of behavior is condoned or authorized is just absurd.”

But Homeland Security ranking member Susan Collins (R-Maine) seemed to imply in her questioning that Sullivan was either naive or in denial about a widespread cultural problem in the Secret Service.

After the hearing, Collins told reporters she was “disturbed” by Sullivan’s repeated assertion that the Colombia romp was an isolated incident, despite reports and indications to the contrary.

“I think that the director is a very fine individual who is very proud of his own career — understandably so — and of the agency that he heads,” Collins said. “Therefore I think he has a difficult time coming to grips with the fact that he has a broader problem than just this one incident.”

At the hearing, Chairman Joe Lieberman (I-Conn.) revealed that there have been 64 reports of sexual misconduct in the Secret Service in the past five years, with most coming from people sending sexually explicit messages or material from government computers. However, there was at least one complaint of “nonconsensual sex.”

Lieberman said the only way Sullivan can address the problem is to come to terms with it.

“This is like a wound to a body, and we’ve got to get in it, find out what happened and clean it out and then let it heal,” he said.

Sullivan did not deny the facts of the Colombia case. And in his most anticipated testimony since he answered questions in 2009 after White House gatecrashers Tareq and Michaele Salahi gained unauthorized access to a private state dinner, he apologized publicly for the first time.

“I am deeply disappointed, and I apologize for the misconduct of these employees and the distraction that it has caused,” he said.

The facts of the case were never in dispute. Senators used the balance of the more than two-hour hearing to bring attention to what they described as a reckless culture in which sexual encounters while on assignment are encouraged, or at least condoned.

Lieberman and Collins were joined by Sens. Tom Carper (D-Del.), Scott Brown (R-Mass.), Rob Portman (R-Ohio) and Ron Johnson (R-Wis.), who all said it seems unbelievable that the Colombia incident was the first of its kind.

Collins dug in on the fact that the agents who brought prostitutes to their hotel and registered them as guests did so under their real names.

“It suggests to me that the agents were so unconcerned about being caught or about the impropriety of their actions that they didn’t even seek to conceal it,” she said.

Sullivan said he is as dumbfounded by the agents’ brazen actions as the Senators.

“I just think between the alcohol and, I don’t know, the environment, that these people did some really dumb things,” he said. “I have no excuse for those actions. All I can tell you is we acted quickly and brought them back here and initiated the investigation.”

Senators were quick to highlight the potential danger of the behavior. Collins suggested that the prostitutes could have been foreign agents or in the pocket of drug cartels, human traffickers or terrorists and could have compromised the president’s safety.

“It’s somewhat ironic that we can be relieved that the women, for the most part, were only prostitutes,” she said. “Obviously it would have been more troubling if they were foreign agents or associated with drug cartels or other foreign gangs.”

Sullivan assured the Senators that no sensitive information was compromised and that the prostitutes did not know the agents were part of the Secret Service.

The internal investigation is ongoing. Sullivan said he is not yet ready to release any new information pertinent to that investigation.

Testifying alongside Sullivan was Department of Homeland Security acting Inspector General Charles Edwards. Edwards, for the first time, said he would conduct an independent investigation of the scandal rather than simply reviewing the internal Secret Service investigation once it concludes.

Edwards said he expects the inquiry to be complete by the fall.

Lieberman and Collins agreed that the outside investigation would be a significant step.